1. Field of the invention
The present invention relates to a boat keel which can be retracted completely from the water by a hinged action. The keel has high aspect ratio and causes a large shift in position of boat center-of-gravity upon retraction.
2. Description of the Prior Art
Retractable keels normally retract straight upward. These are usually called centerboards. Serfess offers a hinged keel which does not retract completely out of the water. The Serfess keel hinges with the hinge point essentially directly over the position of the fully dropped keel. The result of retracting is a rearward movement of the keel center-of-gravity which is something less than half the length of the keel projection below the hull.
Potter's keel operating system is used to allow various positions to optimize sailing performance and to allow keel "pop-up" if the keel strikes something.
Potter uses a vertically positioned cylinder and his keel is pivoted so that it falls down to complete its downward movement. Reedman mentions a plywood centerboard, something of near-neutral buoyancy which in movement to various positions would have little effect on the location of the boat center of gravity. The Readman centerboard pivot is forward of the keel trailing edge. The centerboard movement is sealed on the top of its casing in the hull. Lake's invention does not involve a keel nor does it involve a change in the fore-aft weight distribution of the boat.
Schermerhorn has a hinged centerboard which is designed to maintain a constant boat center of gravity location as the centerboard is raised or lowered. His pivot is forward of the trailing edge and at of the center-of-gravity of the centerboard only about three-eighths of a chord length.